Various types of feed mechanisms exist in the machine tool industry to automate the loading and/or unloading of workpieces into and out of a machine tool. In this regard, it is desirable with respect to both production speed and safety to automatically place workpieces into the machine tool prior to a machine operation and then to automatically remove the workpieces from the machine tool when the machining operation or operations are complete. The intervention of machine tool operators during the process slows the production time and presents additional dangers to the operator.
Many automated loading and unloading devices are too complex and expensive to justify their use in any but the most elaborate and expensive machine tools. Such loading and unloading mechanisms may include, for example, robotic devices or other programmable or otherwise electrically controlled arms, indexing devices, etc. While needs exist in the industry for these sophisticated and expensive machine tool loading and unloading mechanisms, especially in connection with many high volume machining operations, these solutions to the problems associated with manual loading and unloading operations can be too expensive.
One air operated loading and unloading device that solves many of the problems typical of manual loading and unloading operations is disclosed in U.S. Pat. No. 5,505,584 (the '584 patent), assigned to the assignee of the present invention and the disclosure of which is hereby incorporated herein by reference. Using this device, a workpiece may be unloaded and/or loaded via a concentric tubular arrangement. The tubes rotate with respect to each other using a mechanism to facilitate either an unloading operation or a loading and unloading operation with respect to a machine tool spindle. Improvements related to simplifying the rotating mechanism are desirable.
Another air operated loading and unloading device that solves many of the problems typical of manual loading and unloading operations is U.S. Pat. No. 6,202,523 (the '523 patent), assigned to the assignee of the present invention and the disclosure of which is hereby incorporated herein by reference. This device includes a base adapted to be mounted adjacent the machine tool and a tubular member mounted for rotation with respect to the base. The tubular member includes an inner chamber and an elongated opening communicating with the inner chamber for receiving the workpiece. The inner chamber includes one end adapted to communicate with a spindle of the machine tool. A sealing member is mounted for selective removal from the tubular member and for selective, sealing engagement around the elongated opening. As the sealing member is removed from the tubular member, the tubular member may be rotated using a mechanism to unload the workpiece. Again, improvements related to simplifying the rotating mechanism would be desirable.
Further, machine tools generally must cease operation or stop, or slow significantly, so that an automated unloading device may operate to permit automatic unloading of a workpiece. Such stopping or significant slowing is generally necessary to prevent or limit the relative rotation of various pieces of the machine tool and the unloading device, thereby avoiding or reducing the generation of heat, wear, etc. in and on the various pieces.
The necessity of stopping or slowing a machine tool has a number of drawbacks. First, unloading times are, in part, based on the time necessary for the machine tool to stop or slow, and waiting for a machine tool to stop or slow generally increases unloading times. Second, constantly stopping or slowing the machine tool increases wear on the motor of the machine tool, thereby reducing motor life, and, third, stopping or slowing the machine tool generally increases the amount of electric power the motor consumes.
For example, the spindle of a lathe may rotate at rates up to, and including, the maximum operating speed of the lathe during machining operations. However, the spindle of a lathe may rotate at reduced rates of below about 75 revolutions per minute (RPM) during an unloading operation, depending on such factors as workpiece material, chuck mating chamfers, etc. Such a reduced rotation rate aids in breaking a workpiece free of the chuck of the lathe, while heat, wear, etc. in and on the various pieces is reduced to an acceptable level.
Improvements related to increasing the rotation rate of a machine tool during the automatic unloading of a workpiece are desirable.
Improvements related to the machine tool industry, and more specifically related to air operated loading and unloading devices therefore continue to be necessary.